We'll have to wait and see how they're implemented, but I think it might be like in LEGO Harry Potter where characters occupy a single slot in the grid, but rotate through several alternate costumes... And I say this because there aren't enough Iron Man-shaped outlines to fit all the alternates we know he will have, but there are just enough for Iron Man, War Machine and one or two other armored foes. Which means there might be even more characters than we previously believed, if TT aren't counting alternates!